Going from Kars to Georgia

Hello

We are 2 guys who are taking the Dogu express to Kars, arriving at 8pm the 30.03. We are looking to travel further on to Georgia either on the 31.03 or the 01.04. Looking to go to Kutaisi (if it is nice there) and Tbilisi after that. Can someone recommend a bus company or other reasonable priced transport to go there by? We are students with limited economy. Any help is appreciated :)